The use of plastic junction boxes for making electrical connections within the frame work of a building, began in the early 1970's if not somewhat prior thereto. The development of romex type electrical cable led the way to the development of the plastic junction box and for many reasons it has become the preferable device utilized in the field.
The cables are routed into the interior of the box for subsequent hook up with switches, socket outlets and the like. Knock-outs are positioned at the intersection of a rear wall of the box with the top and bottom walls.
A typical cable will include two (2) insulated wires and a ground wire. When introduced into the rear of the junction box, the connections to the particular electrical device, for example, a switch or outlet, are normally effected at the rear of these devices. As such, the wires and the associated wire nut(s) are bunched at the rear and remain there after the placement of the outlet fixture in the wall cavity.
In many circumstances, multiple switches and/or sockets can be located in one junction box. This is accommodated through the ganging of the outlet devices into a single box which is expanded in width to accommodate the additional items.
The junction boxes are secured to the framing members that support the wall structure. Typically, these are vertical stud members which may be of wood or metal construction, the latter particularly used in commercial and institutional construction. These stud members and associated frame members and wall coverings, such as sheetrock, define the wall areas.
The stud members are nominally two inches by four inches (2″×4″) (width versus depth). The actual finished wall stud product when made of wood can measure as little as 1 7/16″×3×⅜″. Metal studs run 1⅝″ by 3′/a″. The typical thicknesses for the sheetrock covering for the wall cavity are ¼″ and ½″.
Cables that are to be connected to a particular junction box enter and exit that box through the knock-outs, positioned, once again at the interface between the back wall of the box and the top or bottom wall as required. As the cable runs through the framed building, it is dressed along or through various wall stud and other framing members. When it reaches a particular junction box where a connection is to be made, the cable is dressed along the wall stud approximately dead center, to ensure as required by applicable standards, the outside surface of the cable is not less than 1¼″ from the nearest edge of the framing member.
Of course in dealing with electricity it is important from a personal as well as fire safety point of view that wiring in general be done to the highest standards so as to eliminate potential risks in these areas. It is important that the individuals who work in this area, electrical contractors, bring a breadth of learned knowledge and practical experience which insures consistency and assurances that these high safety standards are met.
These standards and recommended practices and guides have been developed in the United States by the American National Standards Institute. They are contained in a National Code which is reviewed and updated frequently to reflect new thinking, new devices and experiences so that any deficiencies that become apparent as contractors do their work day to day, can be addressed in the latest version of the Code. The standards embedded in the Code, if followed, ensure that contractors as they move from job to job, whether new construction or remodeling, hopefully, are not met with significant surprises requiring work that might not have been foreseen.
One of the particular Code requirements germane to the present invention is set out in Chapter 3, Article 300. This particular Article includes a Section 300.4 describing various techniques necessary to protect against physical damage to conductors including cables. At 300.4(D), it is stated that “the cable . . . shall be installed and supported [(by staples)] so that the nearest outside surface of the cable . . . is not less than 32 mm (1¼″) from the nearest edge of the framing member . . . where nails or screws are likely to penetrate.” And further in Code Section 300.4(D) it is stated that “[w]here this distance cannot be maintained, the cable . . . shall be protected from penetration by nails or screws by a steel plate . . . or equivalent at least 1.6 mm ( 1/16″) thick.”
In the case of connections of a romex cable to a plastic junction box, the cable must be formed by the contractor so as to move off center of the stud member and directed to the location of the knock-outs, again, at the rear wall interface at the top or bottom of the junction box unit. Although no specific distances are set forth in the Code as to the location of the last staple needed to secure the cable to the mid point of the stud member in relation to the junction box, typical experience of the trade locates that last staple approximately 2″ to 4″ from the top (or bottom) surface of the box. As the cable is directed to the knock-outs, it is apparent they are now positioned within this 1¼″ safety space creating the concern addressed by the present invention. Again, the Code recognizes the need to protect cables that fall within this distance from the nearest edge in that they require that the “cable . . . be protected from penetration by nails or screws by a steel plate . . . or equivalent at least 1.6 mm ( 1/16″) thick” as noted above.
Again, junction boxes are typically secured to a particular wall stud. However this framing member also provides support for the anchors used to secure sheetrock. The installation of sheetrock for a building typically occurs after the rough-in of the electrical work including the installation of the various junction boxes. The experience of electrical contractors, suggests that this activity, that is the installation of sheetrock, many times is not as precise and controlled as is necessary to avoid damage to electrical cables and junction boxes. It is not unheard of, that the sheetrock installation will result in the fastening members, typically metal screws designed for that purpose, are not precisely located along the center line of the supporting stud. Further, they can vary in length based on the work habits of the installer.
The junction box presently utilized in the trade is typically made from thermoplastic material. For so-called “deep boxes”, the depth of the box runs 3.375″. Around the perimeter of the boxes are two molded, visible guidelines set back either ¼″ or ½″ from the front face. These guidelines inform the electrical contractor where to position the junction box in relation to the front face of the stud members so that the face of the box is flush with the outside surface of the sheetrock when installed. Placement of the box in the wall cavity is approximate at best.
In a circumstance where ¼″ sheetrock is to be applied, the deep box in effect would protrude into the wall cavity 3½″ from the outside face of the wall stud member. Although these wall stud members are nominally 3½″ in depth, in time, as noted above these studs have been reduced by the manufacturing process to something less than 3½″ and closer to 3⅜″. As such, the outside surface of the rear wall of the junction box can be as close as ¼″ from the inside surface of the sheetrock secured to the stud member at the rear of the junction box. With the thicker (½″) sheetrock material the nominal clearance behind the back surface of the junction box and the inside surface of the sheetrock would be ½″.
A junction box is typically supplied with means for securing the box to the stud member. This includes a fastening member mounting element that is formed as a part of the box in the molding process and is integral with the outside surfaces of the top and bottom walls. As purchased, the boxes typically include fastening members such as nails or screws already in place in the mounting elements on the top and bottom of the box. The mounting elements are sized to securely retain the fastening members as the box is being handled. The location of the mounting elements, as between the front face and back wall of the box, will vary depending on a particular manufacturer, but the basic design is the same.
Any proposed solution to the safety issues arising from the position of the cable(s) as they approach the knock-out entry points of the box, should not increase the installation time as presently experienced. Further, the plastic junction boxes presently employed have been in use for a considerable number of years and meet all the necessary requirements of the trade. So, there is no desire to modify the box itself to accomplish the purposes sought to be achieved by the present invention.
It is therefore a principal object of the present invention to provide a protective shroud in combination with the typical junction box now employed in the trade, that will prevent the penetration of the box and the array of one or more cables connected to the box by sheetrock screws or other fastening members employed in near proximity to the box and cable.
It is another object of the invention to provide a protective assembly that has a minimal impact, if any, on present installation time and costs.
It is still another object to provide a shroud box assembly design that is easily adaptable to accommodate the plurality of junction boxes available in the market.